Method of and means for making castings



Dec. 6, 1960 G. HARRISON METHOD OF AND MEANS FOR MAKING CASTINGS FiledJuly 28, 1955 il iiliw. w

INVENTOR. GEORGE HARRISON ATTOR EY METHOD OF AND MEANSFORMAKING CASTINGSGeorgeiHarrison', ChicagbFIlk ff (6901W. 30th Stti Betwht-Illil FiledJuly 28, 1955, seriNo. 524,900

12 Claims. ((312 -5723) This invention-relates to an apparatusforand amethod of making castings, particularly castings of the type whereinmetal to be cast is built up on a cooled die surface until themetal-reaches the desired thickness.

It is one of the objects of the present invention to provide a method ofmaking a casting'whereby a cooled die is immersed in a bath of liquidmetal to becast and the die is maintained cool so that the liquid metalsolidifies along the cooled die surface and progressively increases 'inthickness as the cooling of the die is continued, until the desiredthickness is reached.

It is a still further object of the present invention to provide amethod of and means for making a metal casting by the progressivesolidification of liquid metal in contact with a cooled die and whereinany excess solidified metal on any part of the casting is removed whilethe casting 'isstill incontact with the mass of liquid metal.

It is a still further object of the present invention to provide amethod of and means for making castings wherein the liquid metal isprogressively solidified to form a casting and wherein solidified partsof the casting are machined to the required dimensions, or are shaped,while other parts of the casting are still being formed by thecontinuing solidification of liquid metal onto portionsof the castingmetal previously solidified.

It is a still further object of the present invention to provide amethod of and a machine for making castings wherein machining or workingoperations are performed on a casting while the casting is immersed in abath of the metal of which the casting was made.

It is a still further objectof the present invention to provide a methodof and means for making a casting wherein the solidified metal of thecasting is displaced by physical action thereon while the solid castingmetal being displaced is still within a bath of liquid metal of the samecomposition as the metal of the casting.

The attainment of the above and further objects of the invention will beapparent from the following specification taken in conjunction with theaccompanying drawings forming a part thereof.

In the drawings:

Fig. 1 is a longitudinal section showing, diagrammatically, apparatusfor carrying out the present invention as a continuous process for"making slugs or the like; 1

Fig. 2 is a diagrammatic section taken along the line 2--2 of Fig. 1 andlooking in the direction of the arrows;

Fig. 3 is a top plan view of the apparatus shown in Fig. 1;

Fig. 4 is a perspective view of a slug made by the apparatus of Fig. 1;

Fig. 5 is a fragmentary view showing a modification of the presentinvention; and

Fig. 6 is a fragmentary sectional view taken along the line 6-6 of Fig.5.

Reference may now behad more particularly to the tates Patent ly facingcavity 8 defined by the outer surfaces of a "ice drawings wherein likereference numerals designatelike parts throughout.

In Fig. 1 there is shown at 1, diagrammatically, the crucible of a metalmelting furnace of known construction. Suitable means, such as, forinstance, gas flames, heat the crucible either to melt the metal thereinor to maintain it in its molten state, as the case may be. The bath ofliquid metal is indicated at 2. The metal in this case is aluminum oranyaluminum alloy. Above the crucible there is mounteda hollow die or mold5 that is' seeured to and carried by an axially rotatable shaft -6 thatismotor drivenat a fixed speed determined by the operator or the settingof the equipment. The die or mold,--in this instance, is shaped formaking strip material and includes a peripherally extending, outwardwall9, and a pair of flanges 10-40 that extend from the wall 9 a distanceequal to the height or thickness of the material to be cast and arespaced apart a distance equal to the width of the material to be cast.The mold has a side opening 15 into which a cooling medium is injected.In this instance, the cooling medium consists of a spray of water thatenters the mold through a pipe 16 carrying a suitable spray nozzle 17 atthe end thereof. The water-is introduced as a spray against the surfacesto be cooled and leaves the interior of the mold, through the opening15, as steam or vapor. It is within the purview of the present inventionto use means other than water for cooling the die, for instance, a blastof air. The die is adapted to be raised o-r'lowered so that the bottomof the die may be immersed below the liquid level of the bath '2.

The portion of-the die or mold 5 that dips Within the liquid metal 2during the rotation of the mold, but excluding the mold cavity 8 and thesurfaces 2222, are coated with a heat insulating refractory material 33to prevent solidification of liquid metal onto those surfaces. Anysuitable heat insulating refractory material may be used. For instance,this coating may consist of an asbestosfibe-r that is impregnated with abinder consisting of a blackstrap molasses such as is used in the makingof molding cores in the metal casting industry. Any other suitable heatinsulating refractory material may be used. The inner surfacesof thoseWalls that do not form the mold cavity are not as effectively cooled asthe adjacent surfaces of the walls of the mold cavity, due to thepresence of annular disks- 18-18 on the inside of the mold or die 5.

Within the crucible 1 and submerged within the molten liquid there ismounted a die-supporting frame 20 carrying a number of cutting tools ordies 21a, 21b, 21c,

21d, 21c, 21] and 21g. The die-supporting frame and V the cutting toolsare made of material which is inert with the liquid metal in which theyare submerged. A suitable material is tungsten carbide. The tools 21scrape against the surfaces 22 at the periphery of the flanges 1010.

The die 5 is immersed in the liquid metal 2 and is slowly rotated by theshaft 6. At the same time, the interior of the die is being cooled. Theliquid metal 2 is maintained 50 to F. above its melting temperature.Metal from the bath 2 solidifies on the die due to the fact that the dieis being cooled. As the die turns,

occurs, then, as the die or mold 5 continues to rotate Patented Dec. 6,1960 to bring the built up portion of the solidified metal to the nextcutting tool 21, that cutting tool cuts away the excess solidifiedmolded metal, leaving the thickness of the solidified metal on the mold5 equal to the height of the flange 10. As the die or mold 5 continuesto turn in the bath of liquid metal 2, there will be furthersolidification of liquid metal onto the previously solidified metal inthe mold cavity 8, which additional solidified metal is cut off by thenext tool 21. This further solidification that occurs on a surface atwhich a out has been taken by one of the tools 2111-21 does not resultin a welding or chemical union of the further solidified metal with thepreviously solidified metal. Therefore, the subsequent cutting action isa comparatively easy action. The rate of rotation of the shaft 6 is suchas to allow enough time for the metal to build up to the full thicknessof the mold cavity 8 as the die 5 turns from a position where a portionon the periphery thereof first enters the liquid, until that pointreaches the cutting tool 21e or 21f. The subsequent cutting tools andthe last cutting tool 21g which is either at or slightly above the toplevel of the liquid in the crucible 1, provide a margin of safety toassure that the necessary thickness of the casting has been attained,and they cut away the excess that may be built up on the previously cutsurface on the casting in the die cavity 8.

A strip of material cast is indicated at 30. This strip moves in adirection to the left as seen in Fig. 2. In order to prevent pulling ofthe strip through the die 5, one or both of the flanges is provided witha series of spaced apart short notches 32 each of which forms a shortprojection or nib at the edge of the strip 30. These nibs interlock withthe die and prevent pulling the strip 30 through the die at a ratefaster than that determined by the rotation of the shaft 6.

If the end product desired is a slug, slugs may be stamped from thestrip 30. This is accomplished by moving the strip 30 through stampingpunch sets 35a-35b which, in this instance, stamp out circular slugs 36each having a central opening 37.

In Figs. 5 and 6 there is shown, in diagrammatic form, a machineembodying the principles of the present invention applied to the castingof individual cup-shaped objeots as intermittnet operations instead ofcontinuous operations. In this instance, a die 40 is mounted at thelower end of a rotatable tube or quill 42 that extends through a bearing43 in a stationary structure 44, the quill or tube 42 being axiallyrotatable and also longitudinally movable. Within the tube 42 there is atube 45. Cooling water is circulated through the die, flowing downwardlythrough the tube 45, thence into the die 40 and out again through thespace between the tube 45 and the tube 42. An L-shaped cutting tool ordie 48, of tungsten carbide or any other suitable cutting material thatis not affected by the liquid aluminum 2 in the crucible 1 is pro vided.The tool 48 has a vertical cutting edge and a radially extendinglongitudinal cutting edge a fixed distance below the die 40 and issupported on a non-rotatable rod 49 that is guided for longitudinalmovement by a bearing in the stationary structure 44 and by a suitableupper guide, not shown, so that the rod is always maintained verticaland in parallelism with the center of the quill or tube 42. The rod 49is supported by a spring 52, the lower end of which rests on thestationary structure 44 and the upper end of which bears against acollar 54 that is locked to the rod 49. Adjacent to its lower end therod 49 has a collar 56 secured thereto which collar is engaged by a ringcollar 58 in the form of a disk secured to the die 40.

When the rotating die 40 moves from its casting position illustrated inFig. 5 to its upper position, the upward movement of the collar 58thereon permits the rod 49 to be moved upwardly by the spring 52 andthereby to raise the cutting tool 48, that tool following the upwardmovement of the die 40 until that tool is above the level of the liquid2 in the crucible 1. At that time the collar 56 engages a stationarystop 60 that limits further upward movement of the rod 49. The die 40continues to move upwardly, carrying with it the casting that has beenformed thereon during its previous immersion in the liquid 2, as will bepresently explained, to a point where the rotation of the die is stoppedand the casting is thereafter stripped from the die 40 and is carriedaway on a chute or the like. The chute may be moved into positionbetween the bottom of the die 40 and the crucible when the die has beenraised to a suflicient height. After the casting has been stripped fromthe die 40 the die is lowered and the rotation thereof is resumed. Assoon as the collar 58 reaches a position below that of the stop 60 itengages the collar 56 on the rod 49 and pushes it downwardly, so thatcontinued descent of the rotating die 40 carries with it the cuttingtool 48, which is not rotating. The cutting tool 48 is thus maintainedat a fixed distance from the die 40. At the same time, cooling water isbeing circulated through the die 40 to keep the bottom and lowerperipheral wall of the die cool. When the die enters the liquid metal 2,solidification immediately commences along the water cooled surface ofthe die. The die is rotated at a considerable speed but below the speedat which centrifugal force would have any considerable efiect on themetal formed thereon. When any part of the periphery or the base of themetal that has solidified around the die 40 reaches a thickness suchthat it engages the tool 48, a machining operation commences whereby thetool 48 machines away any excess metal that has been formed. Those partsof the casting that have not yet been built up to the desired thicknessare not engaged by the die 48 so that the building up of metal on thoseparts continues. After the metal has been formed around the die 40, theentire structure is elevated in the manner hereinabove set forth, andthe rotation of the die stopped, and the casting at the bottom of thedie is stripped therefrom as above set forth.

While I have herein shown a structure wherein the casting is of acylindrical shape, it is, of course, within the purview of the presentinvention to make the casting of the machine of Fig. 5 of any othershape which is a surface of revolution, in which event the die and thecutting tool 48 would be of corresponding shapes.

When solid metal is formed by the progressive solidification of liquidmetal, each particle of liquid metal unites with the subjacent alreadysolidified metal only of the subjacent solidified metal is of the sametemperature as that of the liquid metal solidifying thereon. When thesolid metal which is in contact with the liquid metal is of atemperature less than that of the solidifying liquid metal the liquidmetal will not unite integrally with the metal around which it issolidifying but will merely adhere thereto. This principle is utilizedin the present invention. When the liquid metal first solidifies incontact with the cold die it does not unite with the die but it doesform a layer of metal thereon. This solidified metal is of exactly thesame temperature as that of the liquid metal at the interface betweenthe two. Thereafter, as heat is continuously extracted from theinterface, by the action of the cooling water within the die, eachparticle of metal giving up its latent heat of fusion is at the sametemperature as the temperature of the interface between the solid andliquid metal, and therefore complete union of the metal being built uptakes place. Once a cut is made into the built up metal by the tools 21of Fig. l or the tool 48 of Fig. 5, the interface between the liquidmetal and solid metal of the casting is removed, leaving a new interfacethat is at a temperature slightly below the temperature of the formerinterface, therefore, slightly below the temperature of the liquidmetal. That newly cut surface of the solid metal Within the liquid metalwill now extract heat from the liquid metal in contact therewith tocause solidification of that liquid metal. However, this initialsolidification on that surface is a solidification of liquid metal ontocooler metal and therefore there is no union between the two. As aresult, in the next cutting operation by a subsequent cutting tool 21bthrough 21g of Fig. l or by the subsequent revolution of the die in Fig.5, the force required to remove that subsequently solidified metal isvery small.

I have herein shown the principles of the present invention as appliedto the machining of simple forms during the process of molding of thesame. It is, however, to be understood that the principles of thepresent invention are equally applicable to mold complicated formswithin the teachings of the present invention.

in compliance with the reqiurements of the patent statutes I have hereshown and described a preferred embodiment of my invention. It is,however, to be understood that the invention is not limited to theprecise construction here shown, the same being merely illustrative ofthe principles of the invention. What I consider new and desire tosecure by Letters Patent is:

l. The method of making a metal casting which comprises placing a dieinto a bath of liquid metal to be cast, cooling the die so that theliquid metal solidifies at the wall of the die, and while the die is inthe bath of liquid metal cutting away the excess metal from thesolidified metal on the wall of the die below the top surface of themetal in the bath, and thereby reducing the temperature of the interfacebetween the cut metal and the liquid metal.

2. The method of making a metal casting which comprises placing a dieinto a bath of liquid metal to be cast, cooling the die so that theliquid metal solidifies at the wall of the die, and while the die is inthe bath of liquid metal cutting away in small successive increments theexcess metal from the solidified metal on the wall of the die at theplaces in the bath where the metal has solidified to an excessivethickness while at the same time maintaining the die in the liquid metaland continuing the solidification of liquid metal onto the casting.

3. The method of casting metal which comprises moving a die in a bath ofliquid metal, cooling the die so that the liquid metal solidifies at itscontact with the die and the solidified mass moves with the die andcontinues to build up in thickness, and removing excess solidifiedmaterial from the mass in the bath in small successive increments at anexcessively solidified part thereof as the mass is moving in the bath ofliquid metal.

4. The method which comprises mechanically shaping a metal body by thephysical cutting away of solid metal thereof while the portion of thebody being cut is in a bath of liquid metal of the composition of thebody.

5. The method which comprises mechanically shaping a metal body by thephysical cutting away of solid metal thereof while the portion being cutis in a bath of liquid metal of the composition of the body, and at thesame time cooling the body to cause metal of the bath to solidify on thebody.

6. Metal casting apparatus comprising means for holding a supply ofliquid metal to be cast, a mold immersed in said means with a portion ofthe mold extending into the liquid metal in said means, means forcooling the mold to cause solidification of metal on the portion of themold immersed in the liquid metal, and means in the supply of liquidmetal for cutting away excess metal from the metal that has solidifiedon the mold wall while the mold wall is immersed in the liquid metal.

7. Metal casting apparatus comprising means for holding a supply ofliquid metal to be cast, a mold immersed in said means with a portion ofthe mold extending into the liquid metal in said means, means forcooling the mold to cause solidification of metal on the portion of themold immersed in the liquid metal, means for rotating the mold andmaintaining the same part of the mold continuously immersed in theliquid metal while solidification of liquid metal is taking place on themold, and means for machining away excess solidified metal during saidrotation.

8. Metal casting apparatus comprising means for holding a supply ofliquid metal to be cast, a mold immersed in said means with a portion ofthe mold extending into the liquid metal in said means, means forcooling the mold to cause solidification of metal on the portion of themold immersed in the liquid metal, means for rotating the mold andmaintaining the same part of the mold continuously immersed in theliquid metal while solidification of liquid metal is taking place on themold, and means for machining away excess solidified metal during saidrotation, said metal machining means being also immersed in the liquidmetal being cast.

9. The method which comprises mechanically shaping a metal body by thephysical cutting away of solid metal thereof while the portion of thebody being cut is in a bath of liquid metal of the composition of thebody and is being subjected to cooling action to cause metal of the bathto solidify on the body so that there is a temperature gradient betweenthe bath of liquid metal and the surface of the metal body exposed atthe place of cutting at the instant of cutting, and thereafter removingany of the metal of the bath that solidifies on the previously cut-awayportion of the body all while the body is at a temperature approachingthe melting point of the metal.

10. The method of making a metal casting which comprises maintaining adie in contact with liquid metal to be cast, cooling the die so that theliquid metal solidifies at the wall of the die and the solidified metalis continuously built up as to thickness, and while the thickness of thesolidified metal is being built up continuously and repeatedly gaugingsuccessively dillerent parts thereof as to the thickness of thesolidified metal beyond the desired thickness and removing the excessthickness if any all while continuing the solidification of metal at there mainder of the die in contact with the liquid metal, and repeatedlygauging at the same places on the solidified metal while maintainingeach place that is gauged continuously in contact with the liquid metalbetween successive gauging.

11. The method of making a metal casting which comprises moving a die ina bath of liquid metal and maintaining the die cooled so that the metalsolidifies on the surface of the die and while the die is in the bath ofliquid metal repeatedly severing in the metal bath excess solidifiedmetal from the surface of the solidified metal mass formed on the die.

12. The method of producing a metal casting which comprisesprogressively solidifying liquid metal by its contact with a cooled moldand while the progressive solidification of the metal is still takingplace severing solidified metal from liquid surface of the casting wherethe metal has solidified beyond its desired thickness while the surfacewhere the severance is taking place is in contact with the liquid metal,and after a time interval repeating the same severing operation of solidmetal at the same place where metal was previously severed from thecasting while maintaining the metal surface immersed in the liquid metalbetween successive severing operations.

References Cited in the file of this patent UNITED STATES PATENTS1,025,848 Wagner May 7, 1912 2,118,438 Lawrence et al. May 24, 19382,390,160 Marvin Dec. 4, 1945 2,561,636 Pyk July 24, 1951 2,664,605Beste Jan. 5, 1954 FOREIGN PATENTS 674,691 Germany Apr. 19, 1939

